1. Field of the Invention
The present invention relates to a tournament oil path constituting apparatus having shuttle valves for selecting the highest pressure of a circuit.
2. Description of the Related Art
An apparatus according to the conventional example shown by FIG. 3 is constituted by a pilot valve section 9 for controlling pressurized oil from a pilot pump Pp, a control valve section 10 connected with a plurality of actuators, a first through an eighth pilot path 1 through 8 for connecting the both sections 9 and 10, a tournament section x for selecting the highest pressure of the first through the eighth pilot paths 1 through 8 and a pump control valve 15 for controlling a delivery amount of a main pump Pm.
The pilot valve section 9 is connected with the pilot pump Pp, controls delivery oil from the pilot pump Pp and supplies pilot pressure to the first through the eighth pilot paths 1 through 8.
The control valve section 10 is constituted by a first through a fourth switch valve 11 through 14 connected to the main pump Pm via a neutral path 19 and a parallel path 30. The first through the fourth switch valves 11 through 14 are connected with actuators A, B, C and D. Further, pilot chambers 21 through 28 of the first through the fourth switch valves 11 through 14 are respectively connected with the first through the eighth pilot paths 1 through 8 for conducting pilot pressure from the pilot valve section 9 to the pilot chambers 21 through 28.
The first through the fourth switch valves 11 through 14 constructed in this way maintain illustrated neutral positions in a normal state and discharge the delivery oil from the main pump Pm to a tank T via the neutral path 19.fwdarw.neutral ports 11a through 14a of the first through the fourth switch valves.fwdarw.a tank path 20. Further, when the pilot pressure is conducted to either of the pilot chambers, the switch valve is switched to either of left and right positions and supplies the delivery oil from the main pump Pm from the parallel path 30 to the actuator via the switch valve. Further, return oil from the actuator is discharged to the tank T via the tank path 20.
Further, the tournament section x comprises a plurality of shuttle valves and a tournament circuit is constituted by the shuttle valves. Further, the tournament section x is connected with a first to an eighth branch path 31 through 38 for conducting pilot pressure in the first through the eighth pilot paths 1 through 8. The shuttle valves of the tournament section x select oil at the highest pressure among the conducted pilot pressure and conduct it to a pilot chamber 15a of the pump control valve 15.
As such a tournament section x constructed as described above, for example, there is used one constituted by integrating a plurality of shuttle valves of a poppet type to a single body block or one described in JP-A-61-36568 in which a plurality of plates formed with oil paths and shuttle valves are laminated together.
Meanwhile, an auxiliary pump Ps is connected to a primary pressure port 16 and a supply pressure chamber 15b of the pump control valve 15 and a pump controlling cylinder 18 is connected to a control port 17. Further, a spring s is installed to a side of the pilot chamber 15a and the spring force is exerted on a spool of the pump control valve 15.
The pump control valve 15 constructed in this way is for controlling the delivery amount of the main pump Pm by moving a rod 18a of the pump controlling cylinder 18 and the spool is moved to a position at which thrust caused by the pilot pressure conducted to the pilot chamber 15a, thrust caused by the delivery pressure from the auxiliary pump Ps conducted to the supply pressure chamber 15b and the spring force of the spring s are balanced. Further, the control port 17 is communicated with a side of the pump port 16 or communicated with a side of a tank port 29 in accordance with the switch position of the spool. When the control port 17 and the tank port 29 are communicated with each other, the pump controlling cylinder 18 is moved in the left direction of the drawing by spring force of a control spring 39 installed to the rod 18a. Conversely, when the control port 17 and the pump port 16 are communicated with each other, delivery oil from the auxiliary pump Ps is supplied to a chamber of the pump controlling cylinder 18 and the rod 18a is moved in the right direction of the drawing. Further, the delivery amount of the main pump Pm is controlled in accordance with a position of moving the rod 18a.
Next, an explanation will be given of operation of the apparatus according to the conventional example.
For example, when pilot pressure is supplied to the pilot chamber 21 of the first switch valve 11 and the pilot chamber 24 of the second switch valve 12 via the first and the fourth pilot paths 1 and 4, the first switch valve 11 is switched to a switch position on the right side of the drawing and the second switch valve 12 is switched to a switch position on the left side of the drawing. Therefore, delivery oil from the main pump Pm is supplied from the parallel path 30 to the actuators A and B via the first and the second switch valves 11 and 12. Therefore, the actuator A is rotated either one of directions and the actuator B is rotated in other of directions.
Further, at this occasion, pilot pressures in the first and the fourth pilot paths 1 and 4 are respectively conducted to the tournament section x via the first and the fourth branch paths 31 and 34. With regard to the conducted pilot pressures, high pressure oil is selected by the shuttle valves and the high pressure oil is conducted to the pilot chamber 15a of the pump control valve 15. The pump control valve 15 is switched to a position at which thrust caused by the pilot pressure, thrust caused by delivery pressure of the auxiliary pump Ps conducted to the supply pressure chamber 15b and spring force of the spring s are balanced. When the pump control valve 15 is switched, the rod 18a of the pump controlling cylinder 18 is also moved in accordance with the switch position and the delivery amount of the main pump Pm is controlled in accordance with the position of moving the rod 18a. Further, the delivery oil from the main pump Pm controlled in this way is supplied to the actuators A and B.
According to the conventional apparatus, the first through the eighth pilot paths 1 through 8 and the tournament section x selecting the highest pressure in the first through the eighth pilot paths 1 through 8 are connected via the first through the eighth branch paths 31 through 38 and accordingly, volume of inside of flow path for conducting the pilot pressure is increased by an amount of the volume of the first through the eighth branch paths 31 through 38. Further, the tournament section x and the pump control valve 15 are also connected via a pipe and accordingly, the volume of the inside of the flow path is further increased. When the volume of the inside of the flow path is increased in this way, response of the pilot pressure conducted at the inside of the flow path is deteriorated. As a result, there poses a problem in which switch response of the pump control valve 15 is deteriorated.
Further, when the volume of the inside of the flow path is increased, temperature rise of oil at the inside of the flow path is retarded. Therefore, there poses also a problem in which it takes time in start operation for the oil to reach predetermined temperature and the response during the time period is deteriorated.
Meanwhile, when the volume of the inside of the flow path is large, air is difficult to exclude and there is a case in which air remains when oil is supplied to the circuit. When air remains at inside of the flow path in this way, there poses a problem in which transmission of the pilot pressure cannot be carried out smoothly.
Further, the tournament section x and the pump control valve 15 are separately installed and accordingly, there poses a problem in which the apparatus becomes large-sized.